We propose to study the role of the renin-angiotensin system in the pathogenesis of malignant hypertension using the new canine renin-specific antibody as a blocking agent; the interaction of the renal baroreceptors with arterial and cardiopulmonary receptors in the regulation of renin release; the role of dopamine in the regulation of renin release in the conscious dog using new specific blocking agents; the relative activity of Na-K-ATPase in outer medullary thick ascending limbs of control and DI rats maintained on high and low salt diets; and the level of Na-K-ATPase activity in outer medullary thick ascending limbs in control and in renovascular hypertensive rats.